Parralle, Com or USB??

Hi Guys.

I'm very new to C++ infact I'm still doing the course, but I have a question I hope you can help me with.

I want to write a programm that will recognise a posative signal from a probe i want to make. the probe will simple be a light sensor, and i want that sensor to start a in the program and another sensor in the probe will stop the timer.

What i would like to know is how easy is it to get a port to recognise a simple signal??

Hope you can help and hope you dont mind helping a compleate novice (at the moment)

Andy
MrNovAsked:
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havman56Commented:
if u need any help i may help u out

playing with PC for such kind of activities may not be intresting so go for embedded systems
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mirtolCommented:
Very easy on a serial port if your circuit is right. You need only push one of the handshake lines high and low. Similarly on a parallel port. USB isn't worth looking at for what you wnat to do.

You can then read the handshake line status directly from the appropriate IO port

Technicalitites for RS232:
http://www.beyondlogic.org/serial/serial.htm
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mirtolCommented:
For example, if you used the CTS handshake line and drive it high and low with respect to ground (-5v to +5v will do) you can simply read the status of that line from [bit 4] of your [serial port base address]+6
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MrNovAuthor Commented:
Thats great, Thank you for you help, On the same basis how easy would it be to read a resistance change in the same probe and get that info back throught the ports??
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mirtolCommented:
If you mean actually measure the resistance change - alot harder, all the ports are digital so you would need to digitize the information (A/D converter).

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MrNovAuthor Commented:
Well my idea is to write a programe to check a cameras exposure and shutter speeds, from what you have told me so far the shutter speeds shouldn't be a problem, its the exposure i am going to have fun with.
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mirtolCommented:
It's not really something you would write a program for, it's far more hardware based...

But if you want to persist, you could probably wire something to your soundcard (it does A/D conversion on sound signal) instead as that will give you a 16-bit 48kHz sample rate (if your soundcard isn't ancient).
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havman56Commented:
MRNOV
what mirtol says is absolutely correct....

i feel u can go for microcontroller based one very easy and really helpfor all such activities best is buy some 8051 kit and work on it!!


u can really play waht ever u want ..


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MrNovAuthor Commented:
thanks for your help and advise guys, will try and stick with it and see what the outcome is...lol
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